When a device is part of a wireless network, it is generally necessary for the device to at least periodically listen to what is being transmitted over the wireless channel to determine if anything is intended for that device. In a situation with multiple channels, a device may limit its listening to one channel, or in some cases may listen to multiple channels.
It is also possible for wireless devices to have a low power mode (often called a sleep mode) in which a local device expects to send and receive no signals for a time and so shuts down to save power. However, in such a low power mode, it is often necessary for the local device to monitor one or more channels to determine whether any signals are being transmitted intended for the local device. Unfortunately, the receive mode is a particularly power-consumptive mode for many wireless devices. This is particularly true for some UWB devices where low powered signals are transmitted so that more power is needed to listen for the signals than it takes to transmit them.
This can significantly limit the effectiveness of the low power mode, by requiring the local device to continually power up its receiver in order to determine whether remote devices are directing transmissions its way.
The problems of power consumption can be exacerbated in situations where multiple channels are available and the local device is required to monitor two or more of these multiple channels. In this case the local device must keep its receiver powered up for an extended period of time to monitor several channels.
This can be particularly wasteful when there is no traffic at all on one or more channels. The local device must power up its receiver to monitor a channel over which no one is transmitting.
Accordingly, it would be desirable to provide a lower power way for a local device to monitor available channels that did not require powering up of a full receive circuit. It would also be desirable to provide a low power way for a local device to monitor multiple channels to determine whether there are transmissions over one or more of the channels.